Jonathan Peelle  0:03  
Hi, and welcome to The Brain Made Plain. I'm your host, Jonathan Peelle. And joining me today is Dr. Lauren Whitehurst. Lauren, thanks for being here. 

Lauren Whitehurst  0:12  
Thanks for having me. 

Jonathan Peelle  0:13  
To start with, I wonder if you could just tell us a little bit about your research and the things that you're studying? 

Lauren Whitehurst  0:20  
Yeah, sure. So my basic research interests are surround the role of sleep for cognition. And so a lot of times we think about sleep as this thing that we do in a 24 hour cycle, we fall asleep at night, we kind of disconnect from the world around us, we don't really think about that the brain is very active, it's very active during sleep, we just kind of disconnect from the world and we wake up the next morning, sometimes we feel refreshed. Sometimes we wish we got a little bit more. But you know that that time happens for all of us. It's something that we share. But what's really interesting for me is that there's so many different things happening in the brain, as well as in the body while we're sleeping. And the activity that's occurring during that time has really interesting implications for what happens to us when we're awake, how we interact with the world, how we learn and remember things. And it also has really, really large implications for our general health over our lifespan. So my research kind of focuses on how to understand sleep, what about sleep matters, what makes sleep good, quote unquote, and, and how that can have implications for our general health and our well being as well as more specifically our cognitive health.

Jonathan Peelle  1:39  
When you I don't know what age you sort of got interested in research or started thinking about that, but did you sort of get interested in the brain first, and then, you know, sleep and how that affects cognition? Or was it like you do focus on sleep? And then kind of come to the brain later?

Lauren Whitehurst  1:56  
Yeah, that's such a it's such a good question. So I actually came to sleep really late. I should I came to science actually quite late. I have an interesting kind of trajectory to neuroscience. So I was, I was convinced even throughout most of my undergraduate career, that I was going to be a lawyer. So I came to science quite late. Not until my senior year in college, did I actually take a course that was asleep seminar.

And I took a course that like really just kind of, like, turned my whole ideas around, I really got interested in the brain more broadly. But really kind of what about sleep is interesting. And I think what what really changed it for me was all of the many ways that sleep interacts that kind of interdisciplinary way in which you can study the body through looking at sleep. So I guess I could say, I kind of came to sleep first and then cognition in the brain a little bit later. But I guess in the best way to say that there were intertwined, right, you couldn't really thinking about sleep without thinking about the brain. So I, they kind of happen at the same time for me. 

Jonathan Peelle  3:05  
So one of the things which you kind of touched on, but that always, I think, increasingly, interests me about sleep is the point you touched on about sort of, like losing? Well, sort of sleep as an altered state of consciousness, that a lot of a lot of what sort of, in the classes that I teach a lot of what we talk about in terms of the brain, and kind of how the brain acts relates to processing things in the environment. So we talked about the visual system and how the eyes, you know, the retina first gets the information and it goes to visual cortex, and then we can kind of build up to objects and faces and houses and so on. But but sleep, of course, we're not aware of what's going on, because we're not conscious, sort of like, by definition, you don't have this environmental awareness. And so I do think sometimes it gets shortchanged, you know, just from the broader kind of cognitive neuroscience discussion, because Because of this, you know, lack of awareness. So, I don't know, do you do you find that when you when you think about it, or yourself or talk to people about it, that they, you know, I almost takes them a minute to kind of get into get into it? 

Lauren Whitehurst  4:15  
Yeah, you know, what, it's so funny that you say that because from a from a cognitive neuroscience standpoint, I think you're right from like, the academic, my academic interactions with people who are not sleep researchers. 100%, right. It's kind of like, oh, yeah, and then you sleep and then you wake up and you keep doing the Wake stuff.

That you keep doing the things that matter to the brain. But from like a lay person, or like there's a conversation with regular people that it like, I have never met someone that I told that I was I study sleep and they're like, Oh, no big deal though. No interest. Everyone is like intensely interested. It's like, oh, I have had a sleep sore story right. I think it kind of speaks to the universal nature of my of this discipline and that everyone is interested in the in how it impacts them. They don't really understand because we don't think about it so much as academics, we don't really push it in neuroscience. In our kind of, you know, our, our classwork right that people don't really think about it as much. And they don't really understand what's happening in the brain or at during this time, and how it impacts so much of the rest of their life, so much of their waking experience.

Jonathan Peelle  5:22  
So, where do you think is sort of a good entry point to think about sleep and cognition, either, like, where you started thinking about it? Or where you just think is the most, you know, the most relevant? 

Lauren Whitehurst  5:35  
Yeah, that's a great question. So I can answer that in two ways. So the first way is the way that I sort of thinking about it. So I actually came to sleeping cognition, and graduates in graduate school. So I, my first introduction to it was really to sleep and kind of the biophysical psychological nature of sleep, what it does to our body, what it does the way that we think. And so you can see that's kind of a natural transition to cognition, right.

And really, through the the way you feel when you're sleep deprived, right, so when you don't get enough sleep, I think you might have an acute experience with this after having twins. And don't get enough sleep, just the the universal impact it has on the way that you experience your world that day, you know, the negative aspects that sometimes associated with it, sometimes that euphoria of sleep deprivation, right, the way that you kind of feel so good for a little bit when you're a little bit deprived. And just the way in which it impacts your your experience, the psychology of the impact of the deprivation was really fascinating for me. And that took me down this path of kind of thinking about really, my, my main, most of my work is really thinking about the ways in which we consolidate memories, and so how good sleep or bad sleep. And I define that we can define that in various ways. I think, though, sleep road is very young. So we kind of figure out different ways to define that, but impacts the way that we really experience the world, either our previous experience of the world, how we bring that with us forward into our next day, or how we experience the world in the moment, and how we then incorporate our previous experiences into our moment in sleep seems to be really relevant to how we form memories. And so that's kind of how I I got interested in it was really through that memory, memory consolidation narrative. But then I would say where the where the field is going, or where I where I think we can really start to bring different things together is thinking about sleep outside of just a brain region, and trying to realize really recognize kind of the systems that are engaged in sleep and how that might impact cognition, various types of cognition, a lot of a lot of work so far has been really centered on memory consolidation. But I think there is quite a bit of evidence that's now kind of building up that support fleet for various types of cognitive processes. So I think that's, that's also where it's going a little bit.

Jonathan Peelle  8:10  
So memory consolidation is a term that comes up a lot in different contexts. Can you just give an example of what you mean by that?

Lauren Whitehurst  8:18  
Yeah, just try to give a very, a really simple example. So as we're walking throughout the world, we are engaging various things, right? we're encountering different experiences. And one of the things that our brains are really kind of built to do and are really good at is taking in those those experience building patterns around those experiences. And that's what we call them coding, taking in information from the environment. And then you want to, once we bring that information in, for us to be able to use it later, we have to store it away somewhere, we have to place it in the brain. And in a sense, that that's what we call consolidation, we place it somewhere, so we can utilize it in the long term. And so that storage process in the brain that that taking that information that we learned and putting it away, is what we would consider consolidation. And then later when we're triggered or need to use that information to navigate. Maybe it's something that that that we come across in our world, whether it be let's say information for a test, as you're studying, right, you study that information, you put it away, and now you're triggered by a question on an exam. You say, Okay, let me let me find that information. We retrieve that information and use it but without that storage process without putting that information away in the brain somewhere, we wouldn't be able to even retrieve it later when we remember trigger for it.

Jonathan Peelle  9:35  
So I was interested in what you said about sort of moving from particular brain regions or even particular cognitive tasks towards a more systems level perspective. And I think also, you know, what you said before about people having a really intuitive sense about sleep, how sleep affects them. And I guess you know, if you asked me how I feel, on days when I when I think I'm sleep deprived, it's not like oh my memory reconsolidation is bad. But everything else is normal. Right? It does feel like there are these really broad effects. So, yeah, so how do you think about sleep from it? Like what does "systems level" mean in this context?

Lauren Whitehurst  10:12  
I think it's a hard question to answer. But it's something that I believe my more recent work is trying to tap into in various ways. And so I think when you think when we understand that we don't feel good after we don't sleep, well, it maybe it's cumulative, right? Like maybe one night of bad sleep isn't the worst, you know, you don't feel great, but two nights or three nights of bad sleep really starts to impact you, you start to feel you might have more negative assets, you don't really want to be bothered, you might actually have a shorter fuse, right. So when things happen, you're driving in traffic, and you're not and you haven't slept really well, maybe most days, not a big deal, someone cuts you off. But if you're really sleep deprived, you might have a more enhanced emotional reaction to that might be harder for you to remember things as you're engaging with someone you can imagine, after not getting good sleep, you have a presentation at work. And it's kind of hard for you to remember those things that you that you've been working on for the previous days. And you also might not feel good, maybe you feel a little dehydrated, maybe you're maybe you feel like you're having some like heart palpitations, and your heart's racing a little bit more than it usually does. And so when I think about what happens to the body, when you don't get enough sleep, it's not just impacting your memory, it's not just impacting your, your cognitive capacity, it's really impacting both the body and the brain. And what does that mean for health and cognition? Broadly, but I think, moving from cognition to more kind of health perspective, what does that mean for our, our systems in our body, so what we know is that when we lose sleep, we have our heart, we have impacts on our heart, we have impact on our immune system, this is really relevant right now, during kind of the COVID pandemic, we have impacts to our cognition, we have impacts to the ways in which our body functions like the the homeostatic process, it tries to keep us balanced, our bodies balanced. And so without, without that it's really impacting various systems. And so from my perspective, those various systems feed into cognition, right, so the ways in which our heart change, heart rate changes the way oversleep, how we regulate, that feeds into our body's ability to mobilize energy to do respond to the environment, to take in information from the environment. And so all of those things contribute to the way in which we experience our lives. And so that's kind of what I mean by moving from one system impacting this thing, and really trying to get a really clear understanding of that, which is vitally important, don't get me wrong, it's vitally important to really understand the depth of process to understand depth of process, but it's also really interesting to start putting those things together, how do these things interact with one another, in that eye, understanding just one thing in isolation, only understand that isolation, and then try to place it into a broader, a broader model is really kind of what I hope to do with the work that I'm moving forward in my lab.

Jonathan Peelle  13:17  
That's great. I also, I wonder, too, you kind of brought up this point, a little bit, but it's not really a state versus trait issue. But in a sense, you can have one night of bad sleep, and that can affect, you know, the next day, in terms of like your momentary reactions, or, you know, irritability or cognitive processing. And I, I feel like a lot of what anyway, but I feel like a lot of people might kind of relate to that in a very immediate way. And so like, as someone who doesn't study sleep, I could imagine running a little experiment in my lab and asking people will have, how much sleep did you get last night? And like thinking that that would matter? But then it seems like there's also the potential for a cumulative effect, you know, even just on cognition, because if day by day, this is impacting how you interact with the world and consolidate information than being chronically sleep deprived, it seems like what sort of effect effects your long term learning and representations and sort of how you interact with information.

Lauren Whitehurst  14:20  
Yeah, that's right. And I think that's definitely one of the areas that that I'm really interested in. I've been thinking about quite a bit now. Is, is the expense how I how I think about it is it's almost an equity question, right? So different people have access to really good sleep, different groups of people, populations of people in different individuals have have differential access to good sleep safe environments to feel comfortable in, that they can rest at night. And that has really large implications for that cumulative question that we're talking about, right? How does long term sleep deprivation impact us? Well, a lot of that is Well, how how, how vulnerable are you to long term sleep deprivation as a person and then some of my work now is really starting to ask questions about population level differences and how people might not have the space environments to sleep in might have, you know, different expectations of them from when it comes as it comes to like workload or timing of work, consistent kind of shift work, things like that, that might engage that might impact their ability to really engage restful, restful sleep that's aligned with what their by their biological needs. And that might lead to this, again, not really state versus trait, but this cumulative impact of sleep deprivation on their long term cognitive health.

Jonathan Peelle  15:49  
Yeah, that's really interesting. And it also, I mean, it kind of just demonstrates the broad reaching impact of sleep health, I guess, for so many different areas, but also sort of like all of the complex things that that might impact how well we're sleeping, right. And some of those are maybe physiological and just whatever is going on with my body, but a lot of them might be environmental, or societal or external that, you know, might be more or less modifiable, but in other words, if we wanted to, you know, improve sleep for a group of people, you know, it's, maybe it sounds easy, but I bet it's really hard.

Lauren Whitehurst  16:30  
Yeah. I mean, I think I think, you know, that's one of the things that excites me about sleep is that it is behavioral, in a sense, right? So it can be modified. It's something that's universal, and that we all do it. And it's also behavioral medicine, it I should say, it's universal. And we all do it also is individual lipstick in that we all do it in different ways. But it's behavioral. So it's modifiable. So we can kind of prescribe different types of sleep for different types of people, and hope that that kind of mitigates whatever issues they're having with cognition, for example, or any other broader health outcome. So the idea that it's modifiable is really exciting. But I think it's one of the hardest, it is a very hard behavior to modify behavior modification is not easy, but he means right, if it was, then we would all be exercising all sleeping well, you know, those things that we know are supposed to be good for us. And so it's not easy to modify that to modify it. And so when we're thinking about, you know, anything that's outside of the individual and saying, like, hey, you know, we would like for you to get eight hours of sleep every night, we would like for you to go to bed at this time, like up at this time, really try to take all the take your phone, and your computer screens and all that stuff out of your bedroom, like all of these things that we would that would help us sleep better, are really hard things to to impact. But then when you think about the overarching structural issues that create some of the behaviors that we see on the individual level, like for example, you know, working multiple jobs, right, or certain things that really make it more difficult to engage really good sleep. That's when it's really even harder to think about how you impact that and change that and shift that people can have better outcomes,

Jonathan Peelle  18:12  
right? You can't just tell someone, I think you should get more sleep. So don't work, that second job that you need for your family.

Lauren Whitehurst  18:19  
Exactly. And that's what that's I mean, that's the reality of it. That's the reality of it that I think a lot of it is out. I think a lot of people recognize that sleep makes them feel good. And when they get good sleep, they're more productive the next day, I really do think that is a generally accepted thing. But there's there's competing forces, there's competing forces with sleep all the time. And, and there's this idea that you're not productive when you're sleeping. And so the first thing you want to cut back is on your sleep so that you can be more productive, right? Yeah,

Jonathan Peelle  18:46  
yeah, I'm—you can't see me. But I'm like, shirking and hiding, because I do that, too. Yeah. So on the podcast, I'll point my finger at people and tell them to get more sleep. But yeah.

So So maybe, you know, having talked about this general, these general issues, we could talk about one of your research papers that you shared. So this is a 2016 paper, "Autonomic activity during sleep predicts memory consolidation in humans". And, and maybe, you know, could you could you kind of frame this to start with assuming that, that our listeners don't know autonomic activities and sort of situate that in this systems level perspective that you have.

Lauren Whitehurst  19:29  
Exactly. Yeah. So this is a good example of kind of what we were I was discussing earlier, but when you get bed when you don't have sleep really impacts multiple systems in both the brain and the body. So when we think about the central nervous system, we think about the brain and the brainstem, we think about the different brain regions and how they interact with one another. That's really kind of a systems level approach to the brain. But we also have all of these things that are below the neck. That change as it relates to they have their own circadian rhythms. That means that they are periodic that, you know, her activity changes on a periodic level in a periodic way, such that you have increased activity at certain parts of the day and reduced activity at different parts of the day. You also have, you know, circadian impacts or different changes in immune activity, right, so that you create different types of immune responses at certain times of the day, and they increase or decrease them depending on the time of day. And what that tells me is that that might also correlate or be related to your sleep time. So circadian changes, you know, what happens throughout a 24 hour period of day, it's also really tightly related to sleep, and that we sleep for the most part, many of us at a certain time of day. And so when I think about kind of how these systems change and shift across the 24 hour day, we can start to really focus in on what's happening during the sleep period. And what's happening during the sleep period is that for example, your heart rate or your the activity of the heart, I should say more broadly shifts and changes as a mech as as it relates to two kind of main systems, the the parasympathetic nervous system, and the sympathetic nervous system, which are two of the main kind of regulatory systems guiding the autonomic nervous system. So the parasympathetic system is really associated with our rest and digest system, in any sort of kind of Psych 101 course or intro Cognero course, we think about these two systems antagonistically. But the truth is, is that while the parents in the sympathetic nervous system is really obsessed with rest, and digest, and the sympathetic system is really associated with kind of energy mobilization, increasing blood flow, or we would call fight or flight, they also work synergistically so we can increase both of these systems, we can decrease both of these systems and we connect, they can actually go up and down antagonistic to each other. So

that that system really regulates a lot of the activity of our periphery or everything that below the the central nervous system, everything's back. So when I back to kind of the original question, when I think about what's happening in that below the neck, and also thinking about what's happening in the brain during sleep, we're trying to understand how those two how the brain and the periphery are associated with one another became a really big interest of mine in graduate school. And so in the paper, you looked at a memory task, can you can you kind of talk us through that? Yeah, of course. So this was a really interesting task. It was based out of a previous paper by Denise Chi in 2009, where they looked at this remote associates task. So the role associate staff is a really well known task. It was developed by Sarnoff, Mednick and 1962, I believe that really been used very often in in cognitive and cognitive research really associated with creativity. So the task basically, is you see three different words. And you're asked to find a fourth word that is related to all three of those words. So you can imagine how that's tapping into kind of association processes. And really creativity being able to see the three words create a relationship between between each of those words with a completely with a fourth word, that you're not to, to at all, you have to come up with that kind of in your from your from your own brain. So that's exciting. It's an interesting task. 

Jonathan Peelle  23:21  
Can I just interrupt? Do you have an example of can we play along at home? 

Lauren Whitehurst  23:26  
Yeah, absolutely. That's, that's a great question. So for example, we actually give an example in the paper. So the example of three words would be cookies, 16, and hearts, that so those are the three words cookies, 16, and heart. And your job is to find a, a fourth word that will be related to all three of those words, but in and of itself, so not not a sentence that uses all three of those words, but just a fourth word. So the example for that cookie, 16, and heart the answer to that would be sweet. And so how do you connect these those three words to sweet cookie, their sweets, you can have a sweet 16. And you can also have a sweet heart. Okay. And so another important thing is that the grammar of how those words are related can be very different.

Jonathan Peelle  24:12  
Right, gotcha. Okay. It's tricky!

Lauren Whitehurst  24:17  
it's hard. Yeah. Generally, generally, we give people get about 40%. So if we give people let's say, 10 words, they'll get about four of them have 1010 problems, they'll get about four of them. So it is a really difficult task. It's not something that people are easily doing at home. It's actually quite, it's quite difficult, but it's an exciting task, but I think it really taps into our associational processes really nicely.

Okay, so then what we did in this paper, which we pulled from the paper by Dr. Cai, is we tried to basically create these different memory conditions. And so the first condition was just a novel A no queue condition. So we called it and that just meant that people did the problems, the problems that I just identify, they did kind of those problems exactly the way those problems

Are there was no just basic creative kind of memory problems, good, basic creative associative prophecy, there was no kind of memory condition in the first condition. The second condition is what we call the corner repeated condition. And so in this condition individuals did those 10 problems, they had a period of time, were they a period of what we call incubation time, and during that incubation time, they either had an episode of sleep or they had a wake episode. And then after that period of sleep or awake, they then did the same exact problem that they saw previously. Again, this is kind of a real explicit memory queuing task. So you see exactly the same things, you have a period of incubation, and then they see the same things again.

And then the second memory cued condition, or the third condition total was what we call it a prime condition. And so in this condition, individuals saw the initial problems in the morning, after they saw those initial problems, they did this analogy task, this analogy tasks, they basically saw very traditional kind of fit analogies, you know, like, right out is to pin as a racer is to, and the answer would be pencil. That's a basic analogy, right? And we really wanted people to get these right. So for this, for this particular study, we actually gave them the first letter of the correct answer. So we're really trying to get people to get these analogies, right. They were very simple. And then after that analogy tasks similar to the other conditions, individuals had a period of time where they either were awake, or they slept, again, an incubation period. And then after that, they were tested on new remote associate problems. So the three words and they had to find the fourth word, but those problems, the answers to those problems. So the answer to the fourth, the fourth word that they could find was the same exact answer as to the analogies. So in this that condition, really trying to prime the answers in the evening, using that analogy tasks, so they could remember when the analogy answers, and then to use those answers in a different context in the context of this task, then they were able to do well on that on that prime condition. 

Jonathan Peelle  27:06  
Okay, so now that we understand the task, how did sleep affect affect performance? 

Lauren Whitehurst  27:12  
Yeah, that's great. So what previous the previous study that Kidal project had found is that it was really necessary for individuals to have a slap a magnifier, and nap

types of sleep. So sleep is broken down into non rapid eye movement, sleep, and rapid eye movement sleep, those are the two main types. rapid eye movement sleep is a a period of sleep where the brain is slightly more activated, compared to non REM, there's increased D synchronization across different brain regions. That means that the EEG, it looks like kind of short,

high low frequency waves called Slow oscillations, or delta frequency waves, that are really just a synchronization of neuronal firing across the cortex. So that means that neurons are firing together, and they're also silenced together. And so we really kind of see this really slow wave kind of take over the cortex, really, this wave starts in the frontal cortex and kind of extends throughout the rest of the the cortical areas. And so these two different kind of oscillatory dynamics in a during sleep are associated with different memory outcomes. So the previous study had found that rapid eye movement sleep seemed to be necessary for people to do well. And that primed memory condition that we talked about before. So it looks like the kind of neural dynamics of rapid eye movement sleep allowed for these associational processes to happen without some kind of external influence. Again, because you're sleeping, there was no new information coming in. So you're able to kind of move these these things around, create this associate associational time in the brain that allows things to move from one area to another. And, as a as an outcome when you wake up, you seem to be performed better on that primary memory tasks. For the other memory conditions, but novel conditions there didn't seem to be an impact of sleep at all. And for the repeated memory condition people seem to perform well if they had just non REM sleep.

or if they had both non rem and REM sleep. So it didn't seem to be as as REM sleep dependent, as the other task was.

So that was the previous studies, previous findings. And in that study, they really only focused on the different dynamics of the brain, they really looked only at non rem and REM sleep, they didn't consider what was happening in the body, right, they didn't consider that during sleep, we also have these changes to the periphery. And so in this paper, we were really interested in extending their findings to understand what's going on in the periphery during sleep, and how does that relate to these different memory outcomes. And we focused in on this particular measure called high frequency heart rate variability, that seems to be related to the parasympathetic nervous system. So it seems to be related to kind of this increased increased activation of the parasympathetic nervous system, which makes sense, right during sleep, your your, your going into this kind of rest state, you have increased parasympathetic activation, and that seems to be really associated with better kind of health outcomes after, as I should say, it's associated with good health outcomes that are that are linked to sleep. And so we focus in on that measure, as in this paper. And what we found was that the similar kind of findings, that's non REM sleep and non rem and REM sleep seem to support that explicit memory condition, and that only a nap with REM sleep seemed to support that prime condition. So we were able to replicate the previous findings. And then in addition to that, we found that when we looked at what what about sleep contributed to the the performance outcomes that we saw post sleep, we found that the nap with REM sleep, both minutes in REM sleep, so kind of the central nervous system of the electroencephalographic patterns that happen. So the REM sleep itself was associated with better performance was associated with performance. But high frequency Heart Rate Variability during REM specifically, so the periphery during REM seems to also be associated with better memory performance for both the explicit condition and the Frank condition and accounted for a significant amount of variance in that out in that performance. And so that was really interesting to us. Because before this paper, no one had really made those connections between the periphery and the brain and how they might be kind of interdependent on one another, and also predicting these these performance outcomes.

Jonathan Peelle  32:24  
That's really interesting. So I mean, in my, you know, being a novice in this area, I think, when you talk about REM sleep, or non REM sleep, or sort of like sleep stages based on EEG, I have some, you know, I have some framework for that. But it sounds like what you're saying is, then the peripheral measures really complement those. And so it's not, it's not just like, Oh, it's another way to learn about the same thing that we already measured, the EEG is a complementary system that you're able to tap into, is that right?

Lauren Whitehurst  32:55  
That is right. That's right. And so it doesn't seem to be accounting for the same the same variance in performance, right? So we've shown before that these different kind of EEG measures account for memory performance, we've shown that previously, but in when we add these peripheral measures, we're finding that they're accounting for variance over and above what those measures account for by themselves. Otherwise, it would be a wash, right? If they were counting for the same amount of variance, it would just be a wash, but we're actually finding that they increase the what we know,

Jonathan Peelle  33:25  
How does breathing—sorry, not to pull you down another rabbit hole, but—how does it tie into this in terms of parasympathetic and sympathetic influences on heart rate or so on?

Lauren Whitehurst  33:36  
Yeah, that's really great. So breathing, so you think about the periphery, we think about all these different organs that are in the periphery, right, so your hearts and your lungs are very intimately connected and related to one another. And the ways in which you kind of take in oxygen, you vaccinate oxygenated blood, and that blood then circulates throughout the body, right. And so the heart periodicity, how your heart's beating is related to the oxygen intake. And the ways in which respiration respiration, the rate at which your breathing also impacts the ways in which your heart rate beats. And so the the innervation from the parasympathetic nervous system takes account takes into account both your breathing rate as well as your heart periodicity and how those two things are impacting each other. And so when we're looking at high frequency, heart rate variability, we're actually looking at the impact of respiration, which is innovative to kind of pick the hairs on the sympathetic nervous system on heart rate. And that's kind of the background kind of that that's the science behind what we're trying to extract. we're extracting that as a measure of parasympathetic nervous system activation. But what's really happening is that the way in which we breathe impacts heart periodicity and changes makes it faster or slower, depending on how fast we're breathing.

Jonathan Peelle  34:58  
Because I...my two anecdotal, you know, bits of information or whatever. But one is, you know, if I wake up in the night, and the older I get, the harder it is for me to fall back asleep. So when I was younger, I would wake up and I'd, I'd fall right back asleep, because I was tired. And now, that doesn't happen. But if I'm aware of my heart beating fast, then I usually, you know, try to concentrate on slowing my breathing down and just relaxing and being very, very, like conscious and top down. But that usually seems to then, you know, help me relax and lower my heart rate and then not fall back asleep. And then the other thing is I, I started after years of not doing regular exercise last year, I started running again. And my sleep got, like, well, not immediately, but very soon, I got a lot better, which was great. I mean, I kind of figured that might happen, but I was surprised to see it. So yeah, that was really that was good. So I have to I have to keep that up, I think.

Lauren Whitehurst  35:56  
Yeah, absolutely. Those are really, those are two really great example exactly of how kind of respiration impacts your parasympathetic activation, which then can drive you to feel calm, rested, and calm and able to engage rest. And then the kind of activation while you're running, the breathing and all that stuff is in a sense, it kind of drives your your homeostatic. So to step back and say, sleep is homeostatic. And that if you don't, if you get if you're sleep deprived, and you don't get sleep, your body will drive your sleep, you have this kind of mechanism that will increase your sleep pressure, increase your your need for sleep. So when you're you don't get enough sleep, let's say you stay up, pull an all nighter for a test, or you have you have twins are crying all night. And you need to engage it your body will kind of able to increase its desire to push yourself to sleep. And we call that sleep pressure your home your sleep homeo stat. And the other main influences the circadian rhythm, which we talked I talked about briefly earlier, but it's linked into this as well. But when you exercise that actually kind of drives not on your honor system, but also a lot of things narrowly, right, we know that there's a lot of kind of important implications for exercise on on cell phones, that neural Cell Life, right cellular life. So that also impacts your your desire to want to sleep right using kind of using energy in that way, will also have implications for increasing your homeostatic drive for sleep, and helping you kind of repair and in rejuvenate the body. So both of those things are both, you know, relaxing yourself and breathing deeply, is going to help you kind of impact your sleep, your sleep, and then also exercise throughout the day, especially if you do it within you know, three to four hours before you expect to fall asleep. That's really going to help you kind of put you to sleep at night. So those are two great examples.

Jonathan Peelle  37:51  
So I wonder, before we end I'm going to ask you for just to remind all of us or to tell us about like sleep hygiene, you know, what are the habits and things that we can do that are in our control? To try to have better sleep? And sort of, I guess a part of that is like, have you has the way you've thought about this change? You know, as you've kind of progressed in your research?

Lauren Whitehurst  38:16  
Yeah, you know, I I think every time I think of Yeah, right, my understanding sleep hygiene has changed so dramatically. I would say it's such a hard. I mean, honestly, it's such a hard thing to think about, because back to our earlier conversation about kind of the equity issues around this, right, there's so many structural ways in which it's hard to engage good sleep, that are almost completely out of your control. But in this context, I like to say when sleep is in your control, and you can figure out like when you have, you know, a safe place to sleep at night, when you have control over your day and your schedule, when all of those things are within your capacity, there are some things you could do to help you get better sleep at night, when those things are outside of your control that really goes to kind of activism, political work and that stuff, right. But when it is in your control, when you have the ability to kind of shape your sleep schedule. The first thing I always say is to get rid of guilt around sleep. So I think a lot of people have this kind of productivity, sleep trade off in their mind. So they they're like oh, if I'm sleeping, I'm not being productive. Let me push the boss that I can be more productive. And so one of the first things I always tell people is like get rid of sleep guilt, right? You know, oh, I could be spending more time with this or that I could be working longer, especially when it's around working like get rid of that guilt. It's so important to your overall health to sleep well and so I really advocate for people prioritizing sleep as as you would prioritize exercise as you would prioritize eating well as you would prioritize taking your medications. I advocate for people to get rid of sleep guilts just throw that away. You should not feel guilty for making sleep important to you in For protecting that time as you would anything else that is what's valuable to you. And so I think that's the first thing. And other things that I suggest people to do is really try to keep a regular sleep schedule. So a lot of a lot of us set alarms. So it is up in the morning, like I think you were alluding to, I also encourage people to set alarm, so go to sleep at night, so put an alarm on your phone that says, Hey, it's 11pm, I'm going to go to bed now. And keep that alarm, even if you work till 1115, keep that alarm at 11pm. Because that's going to start to trigger your body's election, I'm tired now, because time back, I'm actually getting tired, just the alarm going off itself could potentially start triggering that for you. So even if you brush your teeth or something like that, go ahead and keep that alarm in your day, because it can help regulate you. And yeah, and I think that there's other things that that have been discussed before, kind of try to keep light out of your bedroom, you know, keep your TV, your phone, your tablets, they have all these new blue light filters, and you can do the wake to night transition on your phone, and all of those things, I actually encourage people to use those tools, definitely engage in those things, try to keep the light and you're coming into your eyes really low when you're sleeping, when you're getting close to sleep time. Light is kind of our most present trigger to be awake. And it used to just be outside light used to be just the sun that would trigger us to be awake. But, you know, over the last couple of decades, we've had this more and more kind of intrusive light in our environments. And so I would, I would say you know, try to keep that out with that you can turn them off when you can especially close to your bedtime. And then I think one of the last important things that I usually say is that if you have a safe place that you let that you sleep, your bedroom, that safe, and it's comfortable for you to sleep, make it the most comfortable, safe, warm place you could possibly think right, so make sure that you set your thermostat to a good temperature so that you're not too hot, not too cold while you're sleeping, keep stressful things out of the bedroom, right? If your phone is a place where you get a lot of alerts, keep that out, keep it away from you as far away from your bed as you possibly can. And really just make that bedroom really soft and warm and inviting as much as you can.

Jonathan Peelle  42:07  
That all sounds like good advice. And I imagine I don't know if there's actually research on this, but but kind of going back to the whole sleep guilt and productivity, you know, trade off. It probably is a false trade off, right? Because, you know if, you know, hopefully, we're all in this life for the long run, and not just for a day or two. And so yeah, maybe tonight, I can get that one thing done by staying up an extra hour or two or pulling an all nighter, but like over the next 10 years was going to make me quote unquote more productive. And and of course, um, you know, maybe we shouldn't be thinking about productivity anyway. And we have to think about other parts of our life like our health and so on. But maybe even if you can't, you know, even if you're forced to think about productivity, I bet taking care of your your sleep and your body in the long run buys us more anyway.

Lauren Whitehurst  42:59  
Oh, for sure. Yeah, there's there is I'm not so sure that the literature on this particular question but there is literature looking at like, you know, what does it mean to save an extra hour versus get that hour sleep and how well you prefer the next day there's there's quite a bit of people who look into that sleep productivity trade off. So there's some literature around that I'm less familiar with it but what I will say just from my background and sleep science that if you if you prioritize your sleep at night, your next day is more productive, whether productive me actually productive on whatever work assignment that you have, or productive in your social life with your relationships productive with generally your health, your you know, your your health and wellness productive with your ability to have energy to navigate that day. Well, so again, thinking about how we define success is really important when it comes to these things. But But I Yeah, from my from from my standpoint, if you prioritize your sleep, you will have better outcomes next day. But also like you said, that cumulative effect across across decades of your life for sure.

Jonathan Peelle  44:07  
Great. Lauren, thank you so much for joining me today. I learned a lot and I'm also encouraged to go get more sleep.

Lauren Whitehurst  44:14  
That's part of my my mission in life. So I'm happy to share that with you and that you can get rid of your sleep go and get sleep when you when you feel your body needs it.

Jonathan Peelle  44:25  
Alright, thanks so much. Thank you have a good one.

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